Circuits for direct fuel injection in internal combustion engines include a pilot operated valve which can be directly connected to a common rail distributing the pressurised fuel to injectors. The valve is normally closed and can be actuated to open a passage and allow egress of the fuel thus allowing the pressure in the injection circuit to be constantly controlled.
Valves are known inter alia comprising a tubular body in which a needle piloted by an electromagnetic actuator obturates or opens the fuel outlet passage. On the opposite side to the passage, a plug is welded to the body and closes it in sealed manner. In normal operation the passage is closed and its closure is ensured by the piloted actuator which applies a closing force to the needle opposing the opening force applied to the needle by the pressurised fuel. It has proved necessary to ensure the closure of the passage in case of malfunction of the actuator for any reason. A compression spring has therefore been arranged in the body, on the opposite side to the passage, the spring permanently acting between the plug and the needle applying to the latter a force for closure of the passage. The spring is calculated so that in case of malfunction of the actuator, the force applied by the spring is sufficient to overcome the opening force applied by the fuel, and thus the pressurised fuel continues to supply the injectors. Valves are known inter alia in which the needle is attached to the magnetic core of the actuator, the spring being compressed between the plug and the said core.
When the valves are assembled, the multiple components must be handled individually and placed in position one after the other. Inter alia, the assembly of the spring and the holding of it in place between the core, the body and the plug is a source of considerable difficulties and requires a large assembly cycle time.
It has become an urgent matter to facilitate the assembly of the valves and reduce the time necessary for it.